Process of preparing uni-directional current carrying devices



Jan. 3, 1933.

P. H. GEIGER 1,892,832

PROCESS OF PREPARING UNI-DIRECTIONAL CURRENT CARRYING DEVICES FiledSept. 10, 1 5

INVENTOR S H wATTQRNEY Patented Jan. 3, 1933 UNITED STATES PATENT OFFICEPAUL H. GEIGER, 0F WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO THE UNIONSWITCH & SIGNAL company, SYLVANIA OF SWISSVALE, PENNSYLVANIA, ACORPORATION OF PENN- PROCESS OF PREPARING UNI-DIRECTIONAL CURRENTCARRYING DEVICES Application filed September 10, 1925. Serial No.55,523.

.#670482, filed Oct. 24, 1923, for process of preparing uni-directionalcurrent-carrying devices, in so far as the subject matter common to thetwo is concerned.-

I will describe one method of preparing such devices, and will thenpoint out thenovel features thereof in claims.

In the accompanying drawing, Fig. 1 1s a view showing, in elevation, oneform of blank ready to be prepared as a uni-directional current-carryingdevice according to my invention. Fig. 2 is a view showing in verticalsection, auni-directional currentcarrying device as it would appear atpne point in a process embodying my invention. Fig. 3 is a view showingacompleted unidirectional current-carrying device constructed inaccordance with my invention.

Similar reference characters refer to similar parts in each of the threeviews.

Referring to the drawing, the reference character A designates a blankof suitable material such as, copper. As shown, thls blank is ofcircular configuration and is provided with a central aperture A,although this particular form is not essential. The

copper blank is chemically cleaned in a suitable manner, as by a sandblast, or by 1mmersing it for an instant in a caustic solution such asan aqueous solution of sodium hydroxide or common lye and afterwardwashing in water to remove the cleansing agent. The blank is then heatedin the presence of air, as in an electric furnace. If the temperature ofthe copper reaches approximately 1040 centigrade, the surface of-theblank assumes a glazed appearance. The temperature of the blank shouldbe so controlled that it is close to and preferably just below thisglazing temperature or, say 101 5 centigrade. The application of heatcauses a layer of red oxide of copper, or cuprous oxlde, to be formed oneach side of the blank. This layer is of comparatively low resistance.The heating process is continued until the cuprous oxide layer issufficiently thick to be mechanically strong. During this process thereis formed also a thin coating of black oxide of copper or cupric oxide,over the outside of the blank. This black oxide coating has acomparatively high electrical resistance.

After a suflicient amount of oxide has been formed on the copper, theblank is transferred immediately to a second furnace which is maintainedat a temperature of about 600 centigrade. In the second furnace theblank gradually cools in the presence of air. I

have. discovered that this gradual cooling to an intermediatetemperature materially improves the asymmetrical properties of thedevice.

When the temperature of the blank has decreased to substantially thetemperature of the furnace the blank is removed from the furnace andsuddenly cooled or quenched, a preferred'method of accomplishing thisbeing to plunge the blank into a spray of cold water or a current ofcold air. The blank now appears as in Fig. 2, in which A is the copperblank, 1 and 1 are the two layers of cuprous oxide, and 2 and 2 are thecoatings of black copper oxide which cover the blank. the oxide coatingsbeing greatly magnified in thickness in this view.

It has been found that a blank prepared in this manner will have thecharacterist c of offering a great deal higher resistance to an electriccurrent flowing from the metallic copper A to the oxide 1 or 1 than tocurrent flowing in the other direction.

Since the resistance of the block oxide is very high it is desirable tomake electrical connection directly with the red oxide coating and withthe copper. To accomplish this result the black oxide is removed fromBoth the black oxide coating 2 and the red oxide coating 1 may besimilarly removed from the other side to permit connection with thecopper member A. I have found it advantageous toapply powdered petroleumcoke to the oxide coating at this stage to decrease contact resistance.

One convenient arrangement for connecting the device to an outsidecircuit is illustrated in Fig. 3. In this view. the aperture A of thecopper disk A is provided with a bolt 6 which is insulated from the diskby means of an insulating sleeve 8. This bolt also carriestwo terminalplates 4 and 4 of some suitable electro-conducting material such ascopper, one of th ese plates being disposed on each side of the disk A.A number of thicknesses of tinfoil or leadfoil 3 are interposed betweeneach plate and the disk for the purpose of securing more perfectcontact. This tinfoil is particularly desirable adjacent the oxidecoating, but may be dis pensed with on the other side of the disk. Thebolt 6 is provided with a nut-6 for clamping the parts rigidly together,it being noticed that insulating washers 5 and 5 are interposed betweenthe bolt head and the nut and the adjacent terminal plates to preventshort-circuiting the device. The connec tions to the external circuitmay then be conveniently made by means of wires 7 and 7* attached toplates 4 and 4, respectively. When assembled in the manner shown in thedrawing the device will offer considerably higher resistance to currentflowing from wire 7 to wire 7 than to current fiowlng'in the oppositedirection.

It has been found that in some cases the asymmetrical properties of thedevices can be improved by repeating the heating process several times.In such cases the blankis oxidized, gradually cooled, and quenched asbefore, the black oxide removed, and the blank is then returned to thefurnace fora second heating after which it is gradually cooled andquenched as before. After each quenching the black oxide is removed, andthis process is repeated till the surfaces attain the desiredcharacteristics, after which the device may be assembled-as describedhereinbefore.

Devices prepared in accordance with my invention maybe used for numerouspurposes, such for examples as charging'storage batteries fromalternating current sources, and operating direct current electricalinstruments from sources of alternating current supply.

Although I have herein shown and described only one process forpreparing unidirectional current-carrying devices embodying myinvention, it is understood that various changes and modifications maybe made therein within the scope of the appended claims withoutdeparting from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. The process of preparing metal for use in a uni-directionalcurrent-carrying device which consists in heating a chemically cleanblank of copper in the presence of air to form cuprous oxide onthe-blank, and quenching the blank.

2. The process of preparing metal for use in a uni-directionalcurrent-carrying device which consists in heating a copper blank in thepresence of oxygen to form cuprous oxide thereon, and quenching saidblank in water.

3. The process of preparing metal for use in a uni-directionalcurrent-carrying device which consists in cleaning a metallic blank,successively heating the blank a number of times to form cuprous oxidethereon, and quenching the blank after each heating.

4. The process of preparing metal for use in a uni-directionalcurrent-carrying device which consists in cleaning a copper blank,heating the blank in the presence of air to a temperature just below theglazing tempera ture to form cuprous oxide thereon, and quenching theblank.

5. In the process of preparing metal for use in a uni-directionalcurrent-carrying device the steps of cleaning a copper blank, heatingthe blank to form oxide thereon, gradually cooling the blank to anintermedi ate temperature, and quenching the blank.

6. In the process of preparing metal for use in a uni-directionalcurrent-carrying device the steps of heating a copper blank in air toform oxide thereon, gradually cooling the blank in air to anintermediate temperature, and quenching the blank in water.

7. In the process of preparing metal for use in a uni-directionalcurrent-carrying device the steps of heating a copper blank in thepresence of air to a temperature just below the glazing temperature,gradually cooling the blank to an intermediate temperature, andquenching the blank.

8. In the process of preparing metal for use in a uni-directionalcurrent-carrying device the steps of heating a metallic blank to formoxide thereon, gradually cooling the blank to substantially 600centigrade, and quenching the blank 9. In the process of preparing metalfor use in a uni-directional current-carrying device the steps ofheating a copper blank to substantially 1015 centigrade, to form cuprousoxide thereon, gradually cooling the blank to an intermediatetemperature, and quenching the blank.

10. In the process of preparing metal for use in a uni-directionalcurrent-carrying device the steps of heating a copper blank tosubstantially 1015 centigrade to form cuprous oxide thereon, graduallycooling the blank to substantially 600 centigrade, and then quenchingthe blank.

11. In the rocess of preparing metal for use in a uniirectionalcurrent-carrying device the steps of heating a copper blank tosubstantially 1015 centigrade to form cuprous oxide thereon, graduallycooling the blank to substantially 600 centigrade in the presence ofair, and then quenching the blank.

12. The process of preparing metal for use in a uni-directionalcurrent-carrying device 1 which consists in cleaning a copper blank,heating the blank in the presence of air to substantially 1015centigrade to form an inner low resistance oxide coating and an outerhigh resistance oxidecoating thereon, gradually cooling the blank in airto substantially 600 centigrade, quenching the blank, removin both oxidecoatings from a portion of the lank, removing only the high resistanceoxide coating from other portions of the blank, and applying finelydivided carbon to said blank.

13. The process of preparing metal for use in a unidirectionalcurrent-carrying) device which consists in heating a metallic lank toform oxide thereon, and then quenching the blank from a temperature ofabout 600 centigrade.

14. The process of preparing metal for use in a unidirectionalcurrent-carryin device which consists in heating a 'metallic blank to aforming temperature to produce oxide thereon,-and then quenching theblank from a temperature substantially lower than the formingtemperature.

15. The process of preparing metal for use in a unidirectionalcurrent-carrying device which consists in heating a metallic blank to ia forming temperature to produce oxide thereon, and then quenching saidblank when- 40 the blank is at a temperature intermediate the formingtemperature and the temperature of the quenching medium.

In testimony whereof I aflixmy signature.

PAUL H. GEIGER.

